It is a well-known fact that it is difficult to let a small child drink from an open drink container such as a cup without spilling the content of the drink container. The small child cannot make all the complex movements that are needed, and is not capable of controlling the extent to which the drink container needs to be gradually tilted in the process. Even if the child is assisted by an adult, it cannot always be prevented that the drink is spilled due to unexpected movements of the child. In order to solve this problem, various types of devices for covering a drink container have been developed, which comprise a housing and a spout, for example, which projects from the cover device and which has at least one drink opening at a free end thereof. When a child wants to drink, she takes the spout in her mouth and keeps the drink container in a tilted position, and as soon as she exerts a suction force on the spout, the drink flows into her mouth through the spout, in a well-controlled manner due to the limited size of the at least one drink opening. Furthermore, when a drink container which is provided with a cover device is held upside-down, or is shaken, for example, the extent to which the content of the drink container is spilled is limited due to the limited size of the at least one drink opening, or there is even no situation of spillage at all, namely when the cover device is equipped with a valve arrangement which is normally closed, and which is adapted to be opened under the influence of a suction force as exerted through the at least one drink opening.
In a cover device which is equipped with a valve arrangement as mentioned, the valve arrangement may be positioned inside the spout or at an appropriate position inside the housing, behind the spout. In any case, the valve arrangement needs to be designed in such a way that a normal suction force as can be exerted by a small child is sufficient for putting the valve arrangement to an open state. On the other hand, the valve arrangement should not open too easily in order to avoid spillage when the drink container which is provided with the cover device is held upside down, or is shaken, for example. The fact is that in such cases, the valve arrangement is subjected to a force which is directed from inside the drink container to outside the drink container, which is the same direction as the direction of a suction force as exerted through the at least one drink opening. Therefore, in prior art solutions, the design of a valve arrangement is based on a compromise between a drinking situation and a situation in which pressure is prevailing inside the drink container. As a result, a child is compelled to exert a rather high suction force, or a leakproof cover device cannot be guaranteed.
U.S. Pat. No. 4,135,513 discloses a nozzle to be inserted in the opening of a nursing bottle or similar container, and which allows drinking by suction but prevents leaking when the bottle is left in any position. In particular, the drinking nozzle consists of an inner, hollow, substantially cylindrical member intended for being introduced in a tightening manner into an opening of a drink container, and an outer nozzle connected with said member protruding from the container opening. Between the cylindrical member and the nozzle, there is a valve seat, the valve body of which is located at a side of the valve seat turned towards the nozzle and is connected with one end of a shaft introduced through the valve seat. The other end of the shaft is connected with a membrane which along its periphery is fixed to the inner end of the cylindrical member. In that way, it is realized that the membrane together with a cover arranged outside the inner end of the cylindrical member define a space which through a bore in the cylindrical member is in connection with the atmosphere. Furthermore, the cylindrical member is provided with openings which connect the interior of the container with the space which is defined by the inner wall of the cylinder, the valve seat, the valve body and the membrane, and the outer end of the cylindrical member above the openings as mentioned is tight-fittingly connected with the free edge of the container opening. Advantageously, the membrane is fixed to the shaft of the valve body under a pre-stress so that the membrane keeps the valve body against the valve seat with a certain pressure.
In use of the nozzle, when by suction there is created an underpressure in the space defined by the nozzle, the valve seat and the valve body, the valve body will be lifted from the seat so that the liquid contained in the space will flow out through the valve seat. The underpressure will eventually be balanced by the valve letting in air after the user removed the nozzle from the mouth.
The tightening obtained between the valve body and the valve seat by means of the pre-stress of the membrane is sufficient for preventing the liquid from flowing out from the container through the valve when the container is placed on the side. When the container is turned upside down and is shaken or pressed together, there are, however, greater forces which act, and the tightening force caused by the pre-stress of the membrane is, in that case, relatively insignificant. The pressure arising in the space when the container is put under pressure will act with a force on the membrane in the direction away from the valve seat, so that the valve body is pressed against the valve seat with a force which increases proportionally with the pressure in the space, as a result of which it is not possible for liquid to flow out of the container.
US 2003/037820 discloses various types of valves for use in conjunction with fluid containers or tubing. Among other things, a tubing having a valve member which includes a diaphragm is described. The valve member also includes a port and a plunger. The diaphragm is responsive to an external force supplied by a user, and a movement of the diaphragm in response to the external force places the valve member in an open condition. The plunger has a first end joined to the diaphragm and a second end extending from the lower surface of the diaphragm. The second end of the plunger substantially plugs the port when the valve member is in a closed condition.
In another embodiment of the valve, the valve member comprises a duckbill mechanism. The valve member of this embodiment may be placed in the open condition either via a vacuum pressure or a positive pressure exerted on the sidewall of the tubing. In particular, the valve member comprises a pore member having a central portion which dilates when the valve member is in the open condition. The central portion is at least substantially sealed in the closed condition and responsive to an external force provided by a user wherein the dilating central portion expands to allow a flow of fluid substance to pass therethrough. The central portion includes an inwardly tapered, flexible duckbill. This duckbill has a hinge portion joined to the sidewall of the tubing and a separable slit which is at least substantially sealed when the valve member is in the closed condition. The valve member is responsive to a deflection in the sidewall to open the valve member. To operate the valve member by a vacuum pressure, a user applies a vacuum pressure to a distal end of the tubing. As a result, the sidewalls of the tubing are caused to collapse to some extent, whereby the slit is opened to allow for a flow of fluid.
GB 2 333 770 discloses a closure assembly for a drinking vessel such as a trainer cup, which comprises a lid with a drinking spout extending therefrom. Furthermore, a diaphragm is mounted on the lid, which has a sealing portion for cooperating with a valve seat in order to prevent liquid flow through the spout, and another sealing portion for covering a breather hole. When a user sucks on the spout, the sealing portions are deflected to allow liquid flow through the spout and air flow through the breather hole. In a number of embodiments, the latter sealing portion is an annular lateral flap of the diaphragm, extending outwardly along a relatively small distance.